Compressor construction

ABSTRACT

A reciprocating piston type gas pump with a crankshaft assembled into a crankcase thereof through an opening in the front wall of the crankcase. The crankshaft is journaled in the crankcase by a pair of bearings one of which is received in a blind pocket in the rear wall of the crankcase and the other is received in the opening of the front wall thereof. A drive shaft integral with the crankshaft extends through the opening. A cover plate is received in the opening over the drive shaft and is spaced from the front bearing by a sleeve which controls within close tolerances the working height of a seal interposed between the bearing and the cover plate to prevent fluids from escaping from the crankcase between the drive shaft and the cover plate.

3,827,314 Aug. 6, 1974 COMPRESSOR CONSTRUCTION Duane F. Steele, Tecumseh, Mich.

Tecumseh Products Company, Tecumeh, Mich.

Filed: Feb. 5, 1973 Appl. No.: 329,632

Inventor:

Assignee:

References Cited UNITED STATES PATENTS Maybach et a1. 74/596 Primary Examiner-Samuel Scott Assistant ExaminerF. D. Shoemaker Attorney, Agent, or Firm-Barnes, Kisseller, Raisch & Choate [5 7 ABSTRACT A reciprocating piston type gas pump with a crankshaft assembled into a crankcase thereof through an opening in the front wall of the crankcase. The crankshaft is journaled in the crankcase by a pair of bearings one of which is received in a blind pocket in the rear wall of the crankcase and the other is received in the opening of the front wall thereof. A drive shaft integral with the crankshaft extends through the opening. A cover plate is received in the opening over the drive shaft and is spaced from the front bearing by a sleeve which controls within close tolerances the working height of a seal interposed between the bearing and the cover plate to prevent fluids from escaping from the crankcase between the drive shaft and the cover plate.

22 Claims, 6Drawing Figures PAIENTED MN; 6 I974 13, 827. 3 14 sum 1 OF 3 Fig 1 COMPRESSOR CONSTRUCTION This invention relates to gas pumps and more particularly to positive displacement gas pumps with a piston driven by a crankshaft.

Piston type gas pumps with a crankshaft journaled in coaxial openings extending through both the front and rear walls of the crankcase are known in the art. It is expensive and difficult to provide an adequate seal between the journaled crankshaft and the crankcase which prevents all fluids from leaking from the crankcase throughout the useful life of the gas pump. Provision of such adequate seals is more difficult and usually more expensive in semi-hermetic gas pumps used in refrigeration systems in which the crankscase is in communication with the low pressure or suction inlet side of the gas pump.

Objects of this invention are to provide a piston type gas pump with a crankshaft journaled in a crankcase thereof which can be easily and readily assembled, is of simplified design, and economical manufacture and assembly, and which provides an improved seal between the crankcase and the crankshaft journaled therein.

These and other objects, features and advantages will be apparent from a perusal of the following description and accompanying drawings in which:

FIG. 1 is a vertical center section along the crankshaft axis of a four-cylinder V-block positive displacement piston type gas pump embodying this invention.

FIG. 2 is an enlarged fragmentary sectional view of the crankshaft and front bearing and seal assemblies of the gas pump of FIG. 1.

FIG. 3 is a sectional view on line 3-3 of FIG. 1.

FIG. 4 is a fragmentary exploded view partially in section of the component parts of the front bearing assembly of the gas pump of FIG. 1.

FIG. 5 is a fragmentary vertical section of the gas pump of FIG. 1 with an exploded view of the component parts of the front seal assembly thereof.

FIG. 6 is a fragmentary vertical section of a modified form of a front bearing assembly in the gas pump of FIG. 1.

FIG. 1 illustrates a gas pump 10 with a V-block 12 having two cylinders 14 in each bank 16 thereof. A cylinder head 17 is secured to each bank 16 and a piston 18 is received in each cylinder 14. Pistons 18 are reciprocated in cylinders 14 by a crankshaft 20 drivingly coupled to the pistons by connecting rods 22. Crankshaft 20 is journaled in opposed front and rear walls 24 and 26 of a crankcase 28 and has an integral drive shaft 30 extending through front wall 24. Crankcase 28 has integral side walls 32 extending between front and rear walls 24 and 26 and a circular opening 34 through the bottom thereof. A circular plate 36 for covering crankcase opening 34 is received in a counterbore 38 and retained therein by a snap ring 40 received in a groove 42. A seal is provided between cover plate 36 and crankcase 28 by an O-ring 44 received in a groove 46 in the end face of counterbore 38. A pressure relief valve 48 is connected with high pressure cylinder crossover passages'SO in block 12 and crankcase 28 communicates with low pressure crossover passages 52 in block 12 via a passageway 54 therein.

As shown in FIGS. 1 and 5, crankshaft 20 is journaled in rear wall 26 by a ball bearing 56 received in a blind bore 58 therein which opens only into the interior of crankcase 28. Ball bearing 56 has an inner race 60 press fit on a journal 62 of crankshaft 20 and an outer race 64 received in blind bore 58. To facilitate assembly and increase the service life of bearing 56, there is preferably a slight clearance fit from I/ I 0,000 to 5/ I 0,000 of an inch between outer race 56 and bore 58. This slight clearance allows outer race 64 to slowly rotate with respect to bore 58 at a rate of about one revolution per hour which increases the service life of ball bearing 56. Crankshaft 20 is journaled in front wall 24 by a ball bearing 66 received in a sleeve 68. Bearing 66 has an inner race 70 press fit on a journal 72 of crankshaft 28 and an outer race 74 with a shoulder 76 adjacent one edge thereof received :in sleeve 68 with its shoulder bearing on a flange 80 of the sleeve. Outer bearing race 74 is axially retained in sleeve 68 by the cooperation of shoulder 80 with pins 82 (FIGS. 2 and 3) pressed into holes 84 extending radially through the sleeve. Outer race 74 of bearing 66 can be either press fit in sleeve 68 or if desired received therein with a slight clearance similar to the outer race of bearing 56, to increase the service life of bearing 66.

Sleeve 68 is received in a bore '86 and counterbores 88 and 90 extending through front: wall 24 of crankcase 28. Sleeve 68 has a continuous groove 92 in the outer face thereof and two ports 94 extending therethrough to allow oil draining through passage 54 to return to crankcase 28 through bearing 66. Sleeve 68 is axially retained in outer wall 24 by a shoulder 95 adjacent the inner edge thereof bearing on a flange 96 formed by counterbore 88 and by a cover plate 98 bearing on the outer end of sleeve 68. Cover 98 has an axial hole 100 therein through which drive shaft 30 extends and is retained in firm abutment with the outer end of sleeve 68 by a snap ring 102 received in a groove 104 in counterbore 90. A dust shield 106 is press fit on a cylindrical portion 31 of drive shaft 30 and overlies opening 100 in cover plate 98.

- As best shown in FIG. 2, an oil seal is provided between cover plate 98 and crankcase 28 by an O-ring 108 which is entrapped between the inner face of the cover and a chamfer 110 on an outer edge of sleeve 68. A seal is provided between drive shaft 30 and cover plate 98 by a sealing member 112 which is available from Rotary Seal Corporation, a subsidiary of Sealol Inc. of 7440 West Laurence Avenue, Chicago, Illinois as part No. 4] 322-P l 3 (or equivalent from various seal manufacturers). Sealing member 112 has a continuous neoprene ring 116 urged into sealing engagement with cylindrical portion 31 of drive shaft 30 by a spring steel split ring 118. A continuous carbon ring 120, adapted for sealing engagement with cover plate 98, and neoprene ring 116 are received in a circular retainer 122 over which one end of a coil spring 124 is received. The other end of spring 124 is received in a circular shoe 126 with a generally U-shaped cross section which bears on inner race 70 of bearing 66 and is telescoped over retainer 122. Spring 124 yieldably urges carbon ring into sealing engagement with both cover plate 98 and neoprene ring 116.

Spring 124 has a rather critical working height which must be maintained if sealing member 112 is to function properly. This working height of spring 120 is controlled by the axial distance between the inner face of cover plate 98 and the adjacent face of inner race 70 of bearing 66. Sleeve 68 is designed to control the position of bearing 66 in relation to the inner face of plate 98 and thereby maintain within close tolerances this critical working height while facilitating ease of assembly of bearing 66 and'seals 108 and 112 in compressor 10. By entrapping bearing 66 in a fixed axial position in sleeve 68 and butting plate 98 against the sleeve, the critical working height of seal member 112 is maintained within close tolerances when the component parts are assembled in the crankcase of gas pump 10.

To facilitate assembly of crankshaft 20 in crankcase 12, sleeve 68 and bearings 66 and 56 are subassembled to crankshaft 20 before the crankshaft is journaled in crankcase 12 as shown in the exploded view of FIG. 4. Bearing 66 is inserted into sleeve 68 and retained therein by pins 82 which are press fit into holes 84 thereof. The inner race 70 of bearing 66 is press fit on journal 72 of crankshaft 20 and the inner race 60 of bearing 56 is press fit on journal 62 thereof. This subassembly of the crankshaft with bearings 56, 66 and sleeve 68 thereon is then inserted into crankcase 28 through bore 86 in front wall 24 thereof which has a diameter slightly larger than the maximum diametrical dimension of crankshaft 20 (as at the counterweight portion 21) to allow passage of the crankshaft subassembly therethrough. The outer race of bearing 56 is preferably slidably received in blind bore 58 in rear wall 26 and sleeve 68 is preferably press fit into counterbore 88.

As shown in exploded view in FIG. 5, seal member 112 is assembled over cylindrical portion 31 of drive shaft 30 and O-ring 108 is inserted in counterbore 90 adjacent chamfer 110 on the outer edge of sleeve 68. Cover plate 98 is slipped over drive shaft 30 into counterbore 90 and is urged into firm abutting relation with sleeve 68 by snap ring 102 which is inserted into groove 104 in counterbore 90 and then dust seal 106 is press fit onto cylindrical portion 32 of drive shaft 30.

FIG. 6 shows a modified form of journaling crankshaft 20 in the front wall of crankcase 28 in which a ball bearing 130 is received in the outer wall with its outer race 132 directly received in counterbore 88 and its inner race 134 press fit on an enlarged journal 72 of crankshaft 20. A spacer ring 135 is received in counterbore 90 and bears on both the inner face of plate 98 and the adjacent face of outer race 132 to control within close tolerances the working height of the spring 124 of sealing member 112. The shoe 126 of sealing member 112 bears on the adjacent face of journal 72' rather than on the inner race of bearing 130 as shown in the bearing and seal arrangements of FIGS. 1 through 5. In use, ball bearing 130 is somewhat noisier than bearing 66 since it is larger and, hence, is used only where a slightly noisier gas pump is not objectionable.

The use of a block 12 in compressor which has an imperforate rear wall 26 and only one opening 80 in front wall 24 through which crankshaft extends and can be inserted into crankcase 28 provides a gas pump of economical manufacture which can be easily assembled and decreases the likelihood of fluid leaking from the crankcase 28 since there is only one opening through the end walls thereof The control of the axial position of crankshaft 20 in relation to crankcase 28 through only one bearing 66 and journal 72 facilitates manufacture and assembly of the crankshaft by eliminating the need for spacing journal 62 from journal 72 within close tolerances to assure the correct positioning of the crankshaft within the crankcase in relation to cylinder bores 14. This also eliminates the need for close tolerances in the axial spacing between blind bore 58 and bore in the end walls 26, 24 of block 12. F urthermore, this permits larger tolerances to be used on the axial spacing of the journals of the throws of the crankshaft from journal 72 thereof which also facilitates economical manufacture of the crankshaft. The use of sleeve 68 or ring 112 in cooperation with cover plate 98 and a bearing 66 or provides an economical way of maintaining within close tolerances the critical working height of spring 124 of seal 112 and provides ball bearing and sealing structures which facilitate easy assembly thereof. Maintenance of this critical working height improves the seal between the drive shaft and crankcase 28. Economical assembly of the component parts of this gas pump is also facilitated by the design of crankshaft 20, sleeve 68 and bearings 66 and 58 so that they can be subassembled and then inserted into crankcase 28 through opening 80 in the front wall thereof.

1 claim:

1. In a positive displacement piston type compressor, the improvement comprising a crankcase having front and rear outer walls in generally opposed spaced relation to each other, a crankshaft adapted to be journaled in said front and rear outer walls and having a generally axially extending drive shaft, said rear wall being imperforate and having a blind pocket therein opening only generally axially inwardly of said rear wall into the interior of said crankcase, a first bearing carried by said pocket'in said rear wall and journaling said crankshaft adjacent one end thereof for rotation on its axis in said crankcase, said front wall of said crankcase having an opening therethrough through which said crankshaft can be axially inserted into said crankcase, a second bearing received in said opening in said front outer wall of said crankcase and journaling said crankshaft for rotation on its axis with said drive shaft thereof extending through said opening in said front wall to the exterior of said crankcase, a cover for said opening through said front wall of said crankcase, said cover having an opening therethrough through which said drive shaft of said crankshaft extends to the exterior of said crankcase, and a sealing member adjacent said cover and encircling said drive shaft to prevent fluid from leaking from the interior to the exterior of said crankcase through said cover opening, whereby said crankshaft is journaled in said crankcase and sealed to prevent fluid leakage between said cover and said crankshaft.

2. The combination of claim 1 wherein said first bearing comprises a ball bearing having an outer race which is free to rotate with respect to said pocket.

3. The combination of claim 1 wherein said second bearing has an outer race with a larger outside diameter than the outer race of said first bearing.

4. The combination of claim 2 wherein said first and second bearings each comprise a ball bearing and said second bearing has an outer race with a larger outside diameter than the outer race of said first bearing.

5. The combination of claim 1 wherein one of said bearings is slidably carried by one of said outer walls for generally axial movement in said crankcase, the other of said bearings is retained in the other of said outer walls in axially fixed relationship thereto, and said other bearing is also retained in axially fixed relationship to said crankshaft, whereby said crankshaft is positioned axially in said crankcase by said axially fixed relationships of said other bearing to said crankcase and said crankshaft.

6. The combination of claim 5 wherein said first bear ing and said second bearing each comprise a ball bearing and said second bearing in said other bearing and has an outer race having a larger outside diameter than the outside diameter of the race of said one bearing.

7. In a positive displacement piston type compressor, the improvement comprising a crankcase having front and rear outer walls in generally opposed axially spaced relation to each other, a crankshaft adapted to be jour naled in said front and rear outer walls and having a generally axially extending drive shaft, said rear wall having a blind pocket therein opening only generally axially inwardly of said rear wall into the interior of said crankcase, a first bearing carried by said pocket in said rear wall and journaling said crankshaft adjacent one end thereof for rotation on its axis in said crankcase, said front wall of said crankcase having an opening therethrough through which said crankshaft can be axially inserted into said crankcase, a second bearing re ceived in said opening in said front outer wall of said crankcase and journaling said crankshaft for rotation on its axis with said drive shaft thereof extending through said opening in said front wall to the exterior of said crankcase, a cover adapted to be received in said opening through said front wall of said crankcase, said cover having an opening therethrough through which said drive shaft of said crankshaft extends to the exterior of said crankcase, a spacer received in said opening in engagement with said second bearing and abutting on the inner face of said cover to control within close tolerances the axial spacing between said cover and the adjacent end face of said second bearing, and a sealing member encircling said drive shaft and interposed between said cover and said second bearing to prevent fluid from leaking to the exterior of said crankcase through said opening in said cover through which said drive shaft extends, said sealing member being axially collapsible and expandible and yieldably biased to an axially expanded position, and said spacer in cooperation with said second bearing and said cover maintaining said sealing member in assembly within close tolerances of a predetermined axial working height.

8. The combination of claim 7 wherein said second bearing has an outer race and an inner race with said crankshaft journaled in said inner race thereof, and said spacer comprises a ring with one edge abutting on said cover and the other edge thereof abutting on an adjacent end face of said outer race of said second bearing.

9. The combination of claim 7 which also comprises an O-ring entrapped between said cover and said spacer to prevent a fluid in said crankcase from escaping to the exterior thereof between said opening in said front wall and said cover received therein.

10. The combination of claim 8 which also comprises an O-ring entrapped between said cover and said spacer to prevent a fluid in said crankcase from escaping to the exterior thereof between said opening in said front wall and said cover received therein.

11. The combination of claim 7 wherein said second bearing has an inner race and an outer race with said inner race journaled on said crankshaft, and said spacer comprises a sleeve adapted to be received in said opening in said front wall of said crankcase with an end face thereof abutting on said cover, said second bearing being received within said sleeve with said outer race thereof retained in axially fixed position within said sleeve.

12. The combination of claim 11 which also comprises an O-ring entrapped between said cover and said spacer to prevent a fluid in said crankcase from escaping to the exterior thereof between said opening in said front wall and said cover received therein.

13. The combination of claim 1 wherein said first bearing is slidably carried by said pocket in said rear wall for generally axial movement relative to said crankcase, said second bearing is received in said opening in said front outer wall in axially fixed relationship to said crankcase, and said second bearing is also retained in axially fixed relationship to said crankshaft, whereby said crankshaft is positioned axially in said crankcase by said axially fixed relationship of said second bearing to said crankcase and said crankshaft.

14. The combination of claim 7 wherein said first bearing comprises a bearing having an outer race which is free to rotate with respect to said pocket.

15. The combintaion of claim 7 wherein said second bearing has an outer race with a larger outside diameter than the outer race of said first bearing.

16. The combination of claim l4 wherein said first and second bearings each comprise a ball bearing and said second bearing has an outer race with a larger outside diameter than the outer race of said first bearing.

17. The combination of claim 7 wherein one of said bearings is slidably carried by one of said outer walls for generally axial movement in said crankcase, the other of said bearings is retained in the other of said outer walls in axially fixed relationship thereto, and said other bearing is also retained in axially fixed relationship to said crankshaft, whereby said crankshaft is positioned axially in said crankcase by said axially fixed relationship of said other bearing to said crankcase and said crankshaft.

18. The combination of claim 17 wherein said first bearing is said one bearing and said second bearing is said other bearing.

19. In a positive displacement piston type compressor with a crankcase having a front outer wall with an opening therethrough and a crankshaft adapted to be journaled in said crankcase and having a drive shaft extending generally axially through said front wall opening, the improvement comprising a bearing received in said opening and journaling said crankshaft for rotation on its axis with said drive shaft thereof extending through said bearing, a cover closing said wall opening and having an opening therethrough through which said drive shaft of said crankshaft extends to the exterior of said crankcase, a spacer received in said opening in engagement with said bearing and said cover to control within close tolerances the axial spacing between said cover and said bearing, and a. sealing member encircling said drive shaft and interposed between said cover and said bearing to prevent fluid from leaking from the interior to the exterior of said crankcase through said cover opening, said sealing member being axially collapsible and expandible and yieldably biased to an axially expanded position, said spacer in cooperation with said bearing and said cover maintaining said sealing member in assembly within close tolerances ofi a predetermined axial working height.

20. The combination of claim 19 wherein said bearing has an outer race and an inner race with said crankshaft journaled in said inner race thereof, and said spacer comprises a ring with one edge abutting said cover and the other edge thereof abutting an adjacent end face of said outer race of said bearing.

21. The combination of claim 19 wherein said bearing has an inner race and an outer race with said inner race mounted on said crankshaft, and said spacer com- LII front wall and said cover received therein. 

1. In a positive displacement piston type compressor, the improvement comprising a crankcase having front and rear outer walls in generally opposed spaced relation to each other, a crankshaft adapted to be journaled in said front and rear outer walls and having a generally axially extending drive shaft, said rear wall being imperforate and having a blind pocket therein opening only generally axially inwardly of said rear wall into the interior of said crankcase, a first bearing carried by said pocket in said rear wall and journaling said crankshaft adjacent one end thereof for rotation on its axis in said crankcase, said front wall of said crankcase having an opening therethrough through which said crankshaft can be axially inserted into said crankcase, a second bearing received in said opening in said front outer wall of said crankcase and journaling said crankshaft for rotation on its axis with said drive shaft thereof extending through said opening in said front wall to the exterior of said crankcase, a cover for said opening through said front wall of said crankcase, said cover having an opening therethrough through which said drive shaft of said crankshaft extends to the exterior of said crankcase, and a sealing member adjacent said cover and encircling said drive shaft to prevent fluid from leaking from the interior to the exterior of said crankcase through said cover opening, whereby said crankshaft is journaled in said crankcase and sealed to prevent fluid leakage between said cover and said crankshaft.
 2. The combination of claim 1 wherein said first bearing comprises a ball bearing having an outer race which is free to rotate with respect to said pocket.
 3. The combination of claim 1 wherein said second bearing has an outer race with a larger outside diameter than the outer race of said first bearing.
 4. The combination of claim 2 wherein said first and second bearings each comprise a ball bearing and said second bearing has an outer race with a larger outside diameter than the outer race of said first bearing.
 5. The combination of claim 1 wherein one of said bearings is slidably carried by one of said outer walls for generally axial movement in said crankcase, the other of said bearings is retained in the other of said outer walls in axially fixed relationship thereto, and said other bearing is also retained in axially fixed relationship to said crankshaft, whereby said crankshaft is positioned axially in said crankcase by said axially fixed relationships of said other bearing to said crankcase and said crankshaft.
 6. The combination of claim 5 wherein said first bearing and said second bearing each comprise a ball bearing and said second bearing in said other bearing and has an outer race having a larger outside diameter than the outside diameter of the race of said one bearing.
 7. In a positive displacement piston type compressor, the improvement comprising a crankcase having front and rear outer walls in generally opposed axially spaced relation to each other, a crankshaft adapted to be journaled in said front and rear outer walls and having a generally axially extending drive shaft, said rear wall having a blind pocket theRein opening only generally axially inwardly of said rear wall into the interior of said crankcase, a first bearing carried by said pocket in said rear wall and journaling said crankshaft adjacent one end thereof for rotation on its axis in said crankcase, said front wall of said crankcase having an opening therethrough through which said crankshaft can be axially inserted into said crankcase, a second bearing received in said opening in said front outer wall of said crankcase and journaling said crankshaft for rotation on its axis with said drive shaft thereof extending through said opening in said front wall to the exterior of said crankcase, a cover adapted to be received in said opening through said front wall of said crankcase, said cover having an opening therethrough through which said drive shaft of said crankshaft extends to the exterior of said crankcase, a spacer received in said opening in engagement with said second bearing and abutting on the inner face of said cover to control within close tolerances the axial spacing between said cover and the adjacent end face of said second bearing, and a sealing member encircling said drive shaft and interposed between said cover and said second bearing to prevent fluid from leaking to the exterior of said crankcase through said opening in said cover through which said drive shaft extends, said sealing member being axially collapsible and expandible and yieldably biased to an axially expanded position, and said spacer in cooperation with said second bearing and said cover maintaining said sealing member in assembly within close tolerances of a predetermined axial working height.
 8. The combination of claim 7 wherein said second bearing has an outer race and an inner race with said crankshaft journaled in said inner race thereof, and said spacer comprises a ring with one edge abutting on said cover and the other edge thereof abutting on an adjacent end face of said outer race of said second bearing.
 9. The combination of claim 7 which also comprises an O-ring entrapped between said cover and said spacer to prevent a fluid in said crankcase from escaping to the exterior thereof between said opening in said front wall and said cover received therein.
 10. The combination of claim 8 which also comprises an O-ring entrapped between said cover and said spacer to prevent a fluid in said crankcase from escaping to the exterior thereof between said opening in said front wall and said cover received therein.
 11. The combination of claim 7 wherein said second bearing has an inner race and an outer race with said inner race journaled on said crankshaft, and said spacer comprises a sleeve adapted to be received in said opening in said front wall of said crankcase with an end face thereof abutting on said cover, said second bearing being received within said sleeve with said outer race thereof retained in axially fixed position within said sleeve.
 12. The combination of claim 11 which also comprises an O-ring entrapped between said cover and said spacer to prevent a fluid in said crankcase from escaping to the exterior thereof between said opening in said front wall and said cover received therein.
 13. The combination of claim 1 wherein said first bearing is slidably carried by said pocket in said rear wall for generally axial movement relative to said crankcase, said second bearing is received in said opening in said front outer wall in axially fixed relationship to said crankcase, and said second bearing is also retained in axially fixed relationship to said crankshaft, whereby said crankshaft is positioned axially in said crankcase by said axially fixed relationship of said second bearing to said crankcase and said crankshaft.
 14. The combination of claim 7 wherein said first bearing comprises a bearing having an outer race which is free to rotate with respect to said pocket.
 15. The combintaion of claim 7 wherein said second bearing has an outer race with a larger outside diameter than the outer race of Said first bearing.
 16. The combination of claim 14 wherein said first and second bearings each comprise a ball bearing and said second bearing has an outer race with a larger outside diameter than the outer race of said first bearing.
 17. The combination of claim 7 wherein one of said bearings is slidably carried by one of said outer walls for generally axial movement in said crankcase, the other of said bearings is retained in the other of said outer walls in axially fixed relationship thereto, and said other bearing is also retained in axially fixed relationship to said crankshaft, whereby said crankshaft is positioned axially in said crankcase by said axially fixed relationship of said other bearing to said crankcase and said crankshaft.
 18. The combination of claim 17 wherein said first bearing is said one bearing and said second bearing is said other bearing.
 19. In a positive displacement piston type compressor with a crankcase having a front outer wall with an opening therethrough and a crankshaft adapted to be journaled in said crankcase and having a drive shaft extending generally axially through said front wall opening, the improvement comprising a bearing received in said opening and journaling said crankshaft for rotation on its axis with said drive shaft thereof extending through said bearing, a cover closing said wall opening and having an opening therethrough through which said drive shaft of said crankshaft extends to the exterior of said crankcase, a spacer received in said opening in engagement with said bearing and said cover to control within close tolerances the axial spacing between said cover and said bearing, and a sealing member encircling said drive shaft and interposed between said cover and said bearing to prevent fluid from leaking from the interior to the exterior of said crankcase through said cover opening, said sealing member being axially collapsible and expandible and yieldably biased to an axially expanded position, said spacer in cooperation with said bearing and said cover maintaining said sealing member in assembly within close tolerances of a predetermined axial working height.
 20. The combination of claim 19 wherein said bearing has an outer race and an inner race with said crankshaft journaled in said inner race thereof, and said spacer comprises a ring with one edge abutting said cover and the other edge thereof abutting an adjacent end face of said outer race of said bearing.
 21. The combination of claim 19 wherein said bearing has an inner race and an outer race with said inner race mounted on said crankshaft, and said spacer comprises a sleeve adapted to be received in said opening in said front wall of said crankcase with an end face thereof abutting said cover, said bearing being received within said sleeve with said outer race thereof retained in axially fixed position within said sleeve.
 22. The combination of claim 19 which also comprises an O-ring entrapped between said cover and said spacer to prevent a fluid in said crankcase from escaping to the exterior thereof between said opening in said front wall and said cover received therein. 